Gas-fired furnace

Abstract

The present invention provides an apparatus and method for operating a cyclone-fired furnace with gas fuel.

Description

[Technical field]

[0001] The invention lies in the field of furnaces for melting mineral material, in particular in the field of furnaces for melting mineral material in a method for producing fibres. [Background technology]

[0002] Cyclone furnaces are well established in the field of mineral smelting processes.

[0003] Existing cyclone furnaces are operated solely or primarily with coal or with other solid or liquid fuels. Coal is particularly useful as a primary fuel in the operation of a cyclone furnace since it produces a slow-burning flame. WO2014057130A1 allows for the optional injection of a secondary gaseous fuel, which constitutes less than 40% of the total fuel energy, at the lower end of the central region of the cyclone furnace to provide the flame therein. The primary fuel used to melt the mineral raw materials is in particulate form.

[0004] No. 3,077,094 discloses a cyclone furnace in which air, gaseous fuel, and optionally raw materials are mixed together before being charged into the furnace. The gaseous fuel is combusted immediately in this configuration.

[0005] WO 2016 / 092100(A1) uses a primary fuel, solid or liquid, to melt the mineral raw materials. A gaseous fuel may be used as a secondary fuel, co-injected with the particulate fuel in a lower section of the cyclone furnace than the primary fuel. This allows the gaseous fuel to combust quickly and preheat the secondary particulate fuel, generating a stable flame in the lower section of the cyclone furnace, near the molten pool. This configuration allows for efficient use of cheap fuels, such as coal, while at the same time providing a high quality melt. In WO 2016 / 092100(A1), a particulate (i.e. solid or liquid) fuel is mandatory as the primary fuel, and the gaseous fuel is only injected in the lower section of the cyclone furnace in combination with the particulate fuel.

[0006] EP 1 944 873 A1 discloses a cyclone furnace for melting mineral materials, in which the primary fuel is particulate, in particular coal. Only particulate fuel is injected from the top of the chamber and is used in the melting stage. Gaseous fuel is introduced in combination with the particulate fuel in the lower section of the furnace with the aim of forming a flame in the upper part of the molten pool. This flame is said to be advantageous for controlling the temperature of the molten pool and, moreover, for controlling the viscosity of the mineral melt exiting the furnace. However, in this document, particulate fuel is mandatory as the primary fuel.

[0007] Coal and other particulate fuels have been widely used in cyclone furnaces for economic reasons, but it is desirable to use gaseous fuels as the sole or primary fuel in order to improve the environmental characteristics of the melting process. In the course of the development of the present invention, a direct replacement of particulate fuels with gaseous fuels using the same furnace equipment was not successful. Gaseous fuels burn much faster than particulate fuels and with shorter flames than coal. This was not feasible because the direct replacement of particulate fuels with gaseous fuels resulted in blockage of the fuel inlet ports due to the formation of slag. The very fast burning rate of gaseous fuels leads to near instantaneous sintering of the mineral raw materials, which causes undesirable blockage of the inlets. Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to provide an apparatus and method using gas fuel in a cyclone furnace to produce a mineral melt, thereby improving the environmental profile of the process while maintaining melt quality and equipment life. [Means for solving the problem]

[0009] The present invention provides a method for melting mineral material, the method comprising the steps of: providing a cyclone furnace, a particulate mineral raw material, a gaseous fuel, and an oxidant; injecting the gaseous fuel into the furnace through one or more first injection ports; injecting the oxidant into the furnace through one or more second injection ports; injecting the mineral raw material into the furnace through one or more third injection ports; combusting the gaseous fuel with the oxidant, thereby melting the mineral raw material, characterized in that each first injection port is spaced from one or more second injection ports at an angle of separation such that, when measured about a vertical axis passing through the center of the cyclone furnace, no first injection port is at an angle of separation less than 20 degrees from any of the second injection ports.

[0010] The present invention also provides a cyclone furnace for melting mineral materials using a gas fuel as the sole or primary fuel, the furnace comprising a furnace body having a body wall, a furnace lid, one or more first injection ports for injecting a gas fuel into the furnace, one or more second injection ports for injecting an oxidant into the furnace, and one or more third injection ports for injecting a mineral raw material into the furnace, the furnace body comprising an upper section, a middle section, and a lower section, the one or more first injection ports, the one or more second injection ports, and the one or more third injection ports inject the gas fuel, the oxidant, and the mineral raw material into the upper section of the furnace, respectively, and each first injection port is spaced from the one or more second injection ports at an angle of separation such that, when measured about a vertical axis passing through the center of the cyclone furnace, no first injection port is at an angle of separation less than 20 degrees from any of the second injection ports.

[0011] The primary fuel of the present invention is a gas fuel. The gas fuel may be natural gas, biogas, shale gas, or other available gas types, or a combination thereof. Preferably, at least 60% of the energy in the process, more preferably at least 80% of the energy, comes from gas fuel. In the present invention, the only fuel may be gas. This has the advantage of reducing or even eliminating particulate fuels such as coal, improving the environmental characteristics of the process.

[0012] Additional burners or electrodes for Joule heating may be provided above the molten pool or may be submerged within the molten pool to help homogenize the melt.

[0013] The oxidant can be air, oxygen, or oxygen-enriched air. Preferably, oxygen-enriched air is used in the present invention, which can be achieved by injecting oxygen into the feed air. Using pure oxygen allows for a smaller furnace volume but increases the cost of the process, whereas air alone reduces costs but requires a larger furnace volume than oxygen-enriched air.

[0014] The mineral raw material is preferably particulate. Preferably, the raw material particles have a size on the millimeter scale. Preferably, at least 99% of the particles, in particular all particles, are smaller than 4 mm in diameter, and preferably 50% of the particles by weight are smaller than 2 mm in diameter. The composition may be any glass, stone or slag composition generally suitable for forming man-made vitreous fibers (MMVF). Preferably, the composition of the fibers is within the following parameters, calculated as oxides in weight %: SiO2: at least 30, 32, 35, or 37; not more than 51, 48, 45, or 43 Al2O3: at least 14, 15, 16, or 18; not more than 35, 30, 26, or 23 CaO: at least 8 or 10; not more than 30, 25, or 20 MgO: at least 2 or 5; no more than 25, 20, or 15 FeO (including Fe2O3): at least 4 or 5; not more than 15, 12, or 10 FeO+MgO: at least 10, 12, or 15; not more than 30, 25, or 20 Na2O+K2O: zero or at least 1; 10 or less CaO+Na2O+K2O: at least 10 or 15; not more than 30 or 25 TiO2: zero or at least 1; 6, 4, or 2 or less TiO2+FeO: at least 4 or 6; not more than 18 or 12 B2O3: zero or at least 1; 5 or less than 3 P2O5: zero or at least 1; 8 or less than 5 Other: zero or at least 1; 8 or less than 5

[0015] In this method, the furnace may have a structure known as a cyclone furnace, in particular with an upper section, preferably substantially cylindrical, a middle section, preferably substantially frusto-conical, and a lower section, preferably substantially cylindrical, the lower section possibly being provided with a molten pool for collecting and fining the melt.

[0016] The gas fuel, oxidant, and mineral feedstock are all preferably injected at or near the top of the furnace.

[0017] Preferably, each second injection port is integrated with a third injection port such that the oxidant and the mineral raw material are injected together, in which case the gas fuel is separated from both the oxidant and the mineral raw material when injected.

[0018] The gas fuel is preferably injected through the furnace lid.

[0019] Preferably, no additional fuel is injected in the upper section of the furnace.

[0020] Additional gas fuel may be injected through an additional injection port in the lower section of the furnace, usually just above the molten pool. The proportion of energy for the process generated from fuel injected through the first injection port near the top of the furnace is usually at least 40%, preferably 45-55%, in particular about 50%.

[0021] The mineral raw materials and oxidant are preferably injected through the side wall of the furnace body.

[0022] Each injection port for the gas fuel is located at least 20 degrees away from any of the inlets for the oxidizer. This separation ensures that combustion, and the resulting release of heat, occurs slowly enough. The separation angle is measured about a vertical axis through the center of the furnace.

[0023] Injecting the gas fuel through the lid also promotes the separation of the gas fuel and the oxidizer at the moment of injection into the furnace. This separation allows the gas fuel to burn slower with a controlled release of heat energy, so that the mineral raw materials melt inside the furnace rather than sintering at the inlet, which can subsequently lead to blockage of the mineral material inlet. A further advantage to injecting the gas fuel through the lid instead of the sidewall is that wear on the inner walls of the furnace is greatly reduced.

[0024] If the gas fuel is injected through the furnace lid, the gas fuel injection port may be angled 30° to 90° upward from the lid. Lower angles are preferred for better mixing of the gas fuel with the mineral raw materials and oxidizer, so that the gas fuel swirls through the air stream and burns in a controlled manner to melt the mineral raw materials. Very low angles, less than 30°, are not preferred because they require a longer injection lance, especially when thick water-cooled furnace lids are used.

[0025] The gaseous fuel and gaseous oxidant may be provided in a stoichiometric ratio or in a superstoichiometric ratio (excess of oxygen). A volume ratio of natural gas to oxygen-enriched air in the range of 1:4 to 1:15, particularly 1:5 to 1:8, may be particularly suitable for the apparatus of the present invention.

[0026] The gaseous fuel and oxidant may each independently have an injection velocity in the range of 20 to 100 m / sec, preferably 40 to 80 m / sec. The particulate raw material may have an injection velocity in the range of 20 to 60 m / sec, preferably 30 to 40 m / sec. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 shows a schematic top view of a furnace according to the invention. [Diagram 2] FIG. 2 shows a schematic vertical cross-section of the upper part of a furnace according to the invention. [Diagram 3] FIG. 3 shows a schematic diagram of a furnace according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] An exemplary furnace according to the present invention is shown in the figure.

[0029] Figure 1 shows a schematic top view of a furnace 1. A gas fuel injection port 2 passes through the furnace lid 3 with a central exhaust outlet 4. Mineral raw material and oxidant (such as air or oxygen-enriched air) are injected together into the furnace through an injection port 5 located at the top of the furnace 1 body sidewall. The top of the furnace 1, which is generally cylindrical, has a single continuous body sidewall.

[0030] The gas fuel injection ports 2 are spaced at equal angular distances from each other. The separation angle between the gas fuel injection ports 2 is shown in FIG. 1 as angle A. In this case, it is 90° since there are four such injection ports 2 evenly spaced along the circumference of the furnace. The injection ports 5 for the mineral raw materials and the oxidant are spaced at equal angular distances from each other. The separation angle between the injection ports 5 is shown in FIG. 1 as angle B. In this case, it is 90° since there are four such injection ports 5 evenly spaced along the circumference of the furnace. It will be seen that each injection port 5 is spaced at an angular distance of at least 20 degrees from the nearest gas fuel injection port 2. The separation angle between each injection port and the nearest gas fuel injection port 2 is shown as angle C, which in this embodiment is about 45°. The separation angle is measured from the center point of this schematic top view.

[0031] The mineral raw materials, oxidant, and gas fuel are injected tangentially into the furnace 1 and move in a circular flow at or approaching a cyclone system. The location and angle of the gas fuel injection port 2 means that the gas fuel is injected into the oxidant and mineral raw materials flow, promoting slower mixing and energy release as the mineral raw materials melt with the combustion of the gas fuel.

[0032] Figure 2 shows a side cross-sectional view of a furnace 1 according to the invention. The mineral raw material and the oxidant (usually air, oxygen or oxygen-enriched air) are injected together through ports 5. Specifically, in this embodiment, the oxidant is fed through inlet port 5a and the mineral raw material through inlet port 5b, and these two components are fed together into the upper section 1a of the furnace 1. Alternatively (not shown), the raw material can be fed through the lid 3 from a position adjacent to the oxidant inlet port. If oxygen-enriched air is used as the oxidant, this can be achieved by injecting oxygen into the air stream at inlet section 5a.

[0033] The general direction of material flow inside the furnace 1 is also shown in FIG. 2. Gas fuel is injected into the flow provided by the oxidizer and mineral raw materials via ports 2 passing through the furnace lid. Each of the injection ports 2 is positioned at an angle D of 30 to 90 degrees from the furnace lid. This allows delayed mixing as the fuel burns without being suctioned out the exhaust 4 before combustion while the energy released from the combustion of the fuel melts the mineral raw materials. The circulation flow continues as the mineral materials melt and drop down the furnace to the middle section 1b and into the lower section 1c (not shown in FIG. 2).

[0034] Figure 3 shows a schematic view of the exterior of the furnace 1. Shown are a generally cylindrical upper section 1a, a generally frusto-conical middle section 1b, and a generally cylindrical lower section 1c. Ports 5 for mineral raw materials and oxidant, and ports 2 for gas fuel, are located at the top of the furnace 1. Specifically, the gas fuel port 2 passes through the furnace lid 3, and ports 5 for mineral raw materials and oxidant pass through the body side wall of the upper section 1a of the furnace 1.

[0035] Additional heating devices such as further burners or electrodes may be implemented in the middle section 1b and / or the lower section 1c to heat and refine the molten mineral material, but the primary fuel source is gas fuel and the energy for melting the mineral material is provided by gas fuel injected at or near the top of the furnace 1.

[0036] The lower section 1c is provided with an outlet 6 for the mineral melt. In Figure 3, the outlet 6 takes the form of a siphon. Alternatively, the outlet 6 may be provided in the base of the furnace 1 (not shown).

[0037] The melt can be transported to a fiberizer, such as an internal centrifugal device (spinning cup) or an external centrifugal device (cascade spinner), where it can be converted into fibers in a conventional manner and subsequently formed into a mineral fiber product, also in a conventional manner.

Claims

1. 1. A method for producing a mineral melt, comprising the steps of: providing a cyclone furnace, a particulate mineral feedstock, a gaseous fuel, and an oxidant; injecting a gas fuel into the furnace through one or more first injection ports; injecting an oxidant into the furnace through one or more second injection ports; injecting mineral feedstock into said furnace through one or more third injection ports; combusting said gaseous fuel together with said oxidant, thereby melting said mineral raw materials; Including, The gas fuel, oxidant, and mineral raw materials are all injected into the top of the furnace; wherein each first injection port is spaced from the one or more second injection ports at an angle of separation such that no first injection port is at an angle of separation less than 20 degrees from any of the second injection ports, when measured about a vertical axis passing through a center of the cyclone furnace.

2. The method of claim 1 , wherein each second injection port is integral with a third injection port.

3. 2. The method of claim 1, wherein each first injection port is spaced from the one or more third injection ports at an angle of separation such that no first injection port is at an angle of separation less than 20 degrees from any of the third injection ports, as measured about a vertical axis passing through a center of the cyclone furnace.

4. The method of any one of claims 1 to 3, wherein the gas fuel injected through the one or more first injection ports provides at least 40% of the energy in the furnace.

5. A method according to any one of claims 1 to 3, wherein the gas fuel injected through the one or more first injection ports supplies at least 50% of the energy in the furnace.

6. The method of any one of claims 1 to 5, wherein the furnace comprises a body and a lid, and the first injection port passes through the lid.

7. 7. The method of claim 1, wherein the furnace comprises a body having a body wall and a lid, the body comprising an upper section, a middle section, and a lower section, and the second and third injection ports pass through the upper section of the body wall.

8. The method of claim 6, wherein each of the one or more first injection ports is positioned at an angle of between 30 and 90 degrees from the lid of the furnace.

9. The mineral raw material has the following composition in weight percent: Yes ２ :3p~5q A ２ O ３ : at least 14, 15, 16, or 18; or less than 35, 30, 26, or 23 CaO: 8 to 30 MgO: 2 to 25 FeO (Fe ２ O ３ (including): 4-15 FeO+MgO: 10-30 Na ２ O+K ２ O: Until 10 CaO+Na ２ O+K ２ O:10~30 TiO ２ : Up to 6 TiO ２ +FeO:4~18 B ２ O ３ : Up to 5 P ２ O ５ : Until 8 Others: up to 8, The method according to any one of claims 1 to 8, comprising:

10. The method according to any one of claims 1 to 9, wherein the oxidant is air, oxygen, or oxygen-enriched air.

11. 1. A cyclone furnace for melting mineral raw materials, comprising: a furnace body, a furnace lid, one or more first injection ports for injecting a gas fuel into the furnace, one or more second injection ports for injecting an oxidant into the furnace, and one or more third injection ports for injecting a mineral raw material into the furnace; The furnace body comprises an upper section, a middle section, and a lower section; each first injection port is spaced from the one or more second injection ports at an angle of separation such that no first injection port is at an angle of separation less than 20 degrees from any of the second injection ports, as measured about a vertical axis passing through a center of the cyclone furnace; and each of the first injection port, the second injection port, and the third injection port configured to inject the gas fuel, the oxidant, and the mineral raw material, respectively, into the upper portion of the furnace; A cyclone furnace characterized by:

12. 12. The cyclone furnace of claim 11, wherein each second injection port is integral with a third injection port.

13. 13. The cyclone furnace of claim 11 or claim 12, wherein each first injection port is spaced from the one or more third injection ports at an angle of separation such that no first injection port is at an angle of separation less than 20 degrees from any of the third injection ports, when measured about a vertical axis passing through a center of the cyclone furnace.

14. The furnace includes a body wall and a lid, and the first injection port extends through the lid. The cyclone furnace according to any one of claims 11 to 13.

15. 15. The cyclone furnace of claim 14, wherein each of the one or more first injection ports is positioned at an angle of between 30 and 90 degrees from the furnace lid.

16. 16. The cyclone furnace of claim 11, wherein the furnace comprises a body wall and a lid, the body wall comprising an upper section, a middle section, and a lower section, and the second and third injection ports pass through the upper section of the body wall.

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